The Stefan-Boltzman Law states the total radiation emission for any body at a given temperature as: R=ECT4. E is the emissivity of the body, which is the ratio of the total emission of radiation of such body at a given temperature to that of a perfect blackbody at the same temperature. For a blackbody, which is a theoretical thermal radiating object that is a perfect absorber of incident radiation and perfect emitter of maximum radiation at a given temperature, E=1; for a theoretical perfect reflector, E=0; and for all other bodies 0<E<1. C is the Stefan-Boltzman constant with a value of approximately 5.67×10−8 W/m2−K4. T is the absolute temperature of the body in degrees Kelvin.
Every object that has a temperature above absolute zero (that is, −273° Celsius) emits electromagnetic radiation. According to Planck's Equation, the radiation emitted by an object is a function of the temperature and emissivity of the object, and the wavelength of the radiation. Irradiation from an object increases with increasing temperature above absolute zero, and quantum energy of an individual photon is inversely proportional to the wavelength of the photon. The Total Power Law states that when radiation is incident on a body, the sum of the radiation absorbed, reflected and transmitted is equal to unity.
Infrared heating is more efficient than conventional heating by conduction and convection in that infrared irradiation can be used in localized heating by directing heat and irradiation towards only the selected space. Infrared irradiation does not heat the air in the selected space, and only heats the objects within that space. In fact, radiation can be transmitted in or through a vacuum without the need of a medium for heat transfer, unlike conventional heating by conduction and/or convection.